Fluorine-based lubricants are widely used for lubrication of various machines such as vehicles, electric equipments, construction machines, information equipments, industrial machines, working machines, and parts constituting them. With recently increased speeds, decreased sizes, enhanced performances, and decreased weights of these machines, temperatures of the machines and peripherals thereof tend to be increasingly raised.
Further, lower friction and higher wear resistances are demanded for the lubricants because of exemplary reasons to improve manufacturing efficiencies using the various machines and to prolong maintenance intervals of the machines, and stabilizing properties are demanded for the lubricants because the lubricants are desired to be stably used in environments contacted with members having catalytic activities.
To improve high-temperature performances, there is typically adopted a technique to increase a viscosity of a base oil of a lubricant. Although this technique improves a heat resistance of the lubricant, its operability is deteriorated at a low temperature.
Patent Document 1 discloses a phosphonic acid compound containing a perfluoropolyether group as a fluorine-containing group. Such a compound dissolves in a fluorine oil, and is also excellent in lubricating ability. However, it is an actual circumstance that the compound is becoming incapable of satisfying the recently increased demand for stabilizing property.
Patent Document 2 discloses aryl sulfonate and phosphonate compounds each including, or without including, a mono- or poly-alkyleneoxide bonding group between phosphorus and a fluorocarbon group. Since these compounds each include a fluorine-containing group and a phosphoric acid group configured to form a C—O—P bond such that hydrolysis is caused to become inferior in heat resistance and durability, the compounds are disadvantageous in failing to exhibit a heat resistance which is an intrinsic feature of a fluorine oil/fluorine grease.
Patent Document 3 describes a lubricant for magnetic disk, which contains stabilizing compounds constituted of repeating units of —(CF2O)— and groups of CHNRR′. However, expensive methanesulfonyl chloride is required to produce these compounds, and specific reaction manipulation and the like are required then such as a reaction under an anhydrous condition, thereby bringing about a problem that scaling-up of the production to industrial dimensions is not easy.
Patent Document 4 discloses a compound having a pyridine ring, which exhibits an excellent performance for stability of a perfluoropolyether base agent. However, it is suggested that, in a production method to use a phase transfer catalyst and a pyridine derivative to obtain a corresponding fluorine-containing alcohol, there are required esterification and reduction reactions of a corresponding acid fluoride, so that the production method includes multiple stages (Patent Document 5).
Patent Document 6 describes to add an amide-based compound to a perfluoropolyether having a —(CF2O)— group in the presence of graphite or molybdenum disulfide, for improved durability. However, such durability is not sufficient yet in view of the demand in the market, and it is necessary to deal with increasingly severer demands in the market.
On the other hand, rust prevention properties are particularly required for lubricants, among such circumstances that rust prevention effects are demanded for lubricants in case of usage of equipments in seacoast areas and upon overseas transportation of parts, that lower friction and higher wear resistances are demanded for lubricants because of exemplary reasons to improve manufacturing efficiencies and to prolong maintenance intervals, and that lubricants are desired to be stably used in environments contacted with members having catalytic activities.
Patent Document 7 proposes a technique to use a fluorine grease composition for a rolling bearing, having an excellent antirust capability in addition to a durability at high temperatures, in a manner to add a magnesium compound and a volatile rust-preventive agent to the grease composition. Considering embodiments thereof, although benzotriazole is adopted as the used volatile rust-preventive agent to certainly succeed in providing the composition with a rust prevention capability, the adopted volatile rust-preventive agent comprising benzotriazole is apt to be thermally degraded such that usage thereof at high temperatures causes a lifetime of the lubricant itself to be shortened. Further, its solubility in a fluorine oil is low, and thus utilization thereof to a fluorine oil is impossible.
Patent Document 8 discloses carboxyl groups and amide derivatives, as additives having higher solubilities in fluorine oils. Although carboxyl groups and amide groups certainly form protective films for metals to thereby improve rust prevention capabilities, they are insufficient in thermal stability, so that usage thereof at high temperatures fails to continuously exhibit rust prevention effects.
Patent Document 9 discloses a fluorine grease usable from low temperatures to high temperatures, which includes, as rust prevention additives: disodium sebacate; sodium carbonate; and a carboxylic acid derivative containing a perfluoropolyether chain. Although these additives certainly allow for improvement of rust prevention capabilities, the additives are insufficient in usage for fluorine oils and greases to be used at high temperatures, from an aspect of solubilities in fluorine oils and an aspect of heat resistance.
Patent Document 10 proposes a technique to provide a rust prevention property, by a compound containing a perfluoropolyether chain having an aryl triazine end group.
However, the synthesizing process for the compound includes three stages, and thus it is unsuitable for scaling-up to industrial dimensions.
Further, since multiple by-products tend to be caused in the reaction of trichlorotriazine with HOCH2CF2(OCF2)d(OCF2CF2)cOCF2CH2OH for exemplarily obtaining a compound of its Example 8, it is necessary to strictly control the reaction conditions, thereby making it difficult to obtain the targeted substance with a satisfactory yield.
Patent Document 1: JP2003-027079A
Patent Document 2: JP2002-510697A
Patent Document 3: U.S. Pat. No. 6,083,600
Patent Document 4: JP2004-346318A
Patent Document 5: U.S. Pat. No. 3,810,874
Patent Document 6: WO2006/030632
Patent Document 7: JP9-59664A
Patent Document 8: JP2818242
Patent Document 9: JP2006-348291A
Patent Document 10: JP2006-290892A